Confined placental mosaicism for trisomy 14 and maternal uniparental disomy in association with elevated second trimester maternal serum human chorionic gonadotrophin and third trimester fetal growth restriction.

A case of confined placental mosaicism (CPM) and maternal uniparental isodisomy 14 identified after placental karyotype revealed trisomy 14 in a newborn with intrauterine growth restriction (IUGR) and minor dysmorphic features is reported. During the second trimester of the pregnancy, multiple marker screening revealed an increased risk for Down syndrome of > 1 in 10. The maternal serum human chorionic gonadotrophin (MShCG) was markedly elevated at 4.19 MoM. Amniocentesis revealed a normal 46,XX karyotype. Fetal growth restriction has been associated with elevated MShCG and placental aneuploidy with CPM for chromosomes 2, 7, 9 and 16. The present case of CPM for chromosome 14 was also associated with fetal growth restriction and elevated second trimester MShCG, suggesting a common link. Further studies need to be done to determine if indeed elevation of second trimester MShCG is associated with increased risk of CPM. The present case again demonstrates the need to perform placental karyotype in unexplained fetal growth restriction.

Soybean Cyst Nematode Population Development and Associated Soybean Yields of Resistant and Susceptible Cultivars in Minnesota.

The soybean cyst nematode (SCN), Heterodera glycines, is a major soybean yield-limiting factor, and the use of resistant cultivars is one of the most effective means to manage the nematode. During the past decade, a number of resistant cultivars in maturity groups I and II have been developed and made available to growers. A total of 47 resistant cultivars and nine susceptible cultivars were evaluated at 15 SCN-infested field sites and two noninfested sites during 1996 to 1998 in Minnesota. As expected, more nematodes developed on susceptible cultivars than on resistant cultivars. Egg density on susceptible cultivars increased by 1.9- to 10.6-fold during the growing season at 12 sites and did not change at the other three sites. Average egg density decreased over time for resistant cultivars at all sites, except where the initial egg density was low (≤455 eggs per 100 cm3 soil). Nematode reproduction factors (Rf = egg density at harvest/egg density at planting) for individual resistant and susceptible cultivars were highly consistent across the eight sites where initial SCN density was more than 1,000 eggs per 100 cm3 soil. Resistance, however, varied among the cultivars, with the average Rf of individual resistant cultivars across the sites ranging from 0.3 to 1.7. Resistant cultivars produced an average yield of 3,082 kg/ha compared with 2,497 kg/ha by susceptible cultivars at eight of 10 sites where egg density at planting was greater than 700 eggs per 100 cm3 soil. In contrast, no difference in yield was observed between resistant and susceptible cultivars at sites where egg density at planting was lower than 500 eggs per 100 cm3 soil. Yield differences between resistant and susceptible cultivars increased with increasing initial SCN egg density. In six fields infested with initial densities of more than 5,000 eggs per 100 cm3 soil, resistant cultivars produced 28.4% (676 kg/ha) more yield on average than susceptible cultivars. Soybean yield increased when cultivars with increasing resistance to the SCN (lower Rf or females formed on roots) were grown in fields infested with SCN. Average relative yield (yield of a cultivar/average yield of all resistant cultivars at a site) of individual resistant cultivars across all SCN-infested sites ranged from 0.76 to 1.10. Yield consistency of soybean cultivars was low among the different sites, indicating that many other factors affected yield. Our results suggest growing resistant cultivars is an effective method to manage SCN in Minnesota while minimizing yield loss due to SCN.